when i hit 40mph the car start to shake or stutter what wrong with..it feels like its running out of gas when my tank is full

Tires could be unbalanced

Also could be fuel pump going out. Maybe try cleaner?

no tired is balance just got new ones

1 Check the crank sensor to see if it is working OK 2 Look for a water pump leak (I know it sounds nuts but read on) IF the pump is leaking it will drip down on to the crank sensor which will cause a engine sputtering and cutting out. this condition will only be cleared up if the water stops dripping on the sensor ( which you'll have to replace because the coolant [from the water pump leak] will have eaten in to the rubber seals on the sensor. Then you will want to replace the water pump, cause sensors are around $100.00